Regulation Mechanism Research For The Effect Of D-amino Acids On Biofilm Formation Processes

As the isomer of amino acids, D-amino acids could inhibit bacterial biofilm formation and mature biofilm disassembly; however, the mechanisms were unclear yet.This research was amined at the effect of D-amino acids on the bacterial adhesion with the E. coli JM109cells. The cells were cultivated from the LB media containing different concentrations of D-tyrosine acids/different kinds of D-amino acids (D-aspartic acids, D-methionine, D-leucine, D-tryptophan, D-tyrosine and D-arginine). The experiments conducted on the bacterial physicochemical properties, bacterial adhesion forces, and the extended DLVO (XDLVO) theory was used to analyze the thermodynamics mechanism. According to the thermodynamics theory, Lewis acid-base interaction energy played an important role on bacterial adhesion inhibition. The results indicated that the D-amino acids could control the EPS secretion to influence the bacterial adhesion. D-tyrosine (50μM) had the most apparent inhibition, then D-leucine, D-tryptophan, D-arginine, and D-aspartic acids. The mechanisms of different D-amino acids were not identical.Pseudomonas aeruginosa was used for determining the mechanism of different amino acids inhibited on bacterial biofilm formation. Biomasses assays, bacterial motility, EPS, and bacterial auto-aggregation tests were used to analyze the mechanisms. The result showed that D-aspartic acids had insignificant influence on biofilm formation, while D-tyrosine inhibited the bacterial biofilm apparently. Different effect of D-amino acids on bacterial properties (bacterial motility, EPS extraction, etc.), leading to different apperence on biofilm formation (ripening times, biomass, etc.). Besides, principal component analysis (PCA) and hierachial cluster analysis (HC A) results showed that the effect of D-amino acids on bacterial surface might relate to the properties:the effect of nonpolar D-amino acids much more apparent than polar ones, while the neutral ones were more obvious than alkaline and acidic D-amino acids.